Transition in LS-coupling confusion

In summary, the conversation discusses the confusion surrounding transition rules in LS-coupling for a 2 electron system with l1, s1 and l2, s2. The rules for electrons in electric dipole transitions are mentioned, including Δl = +/- 1, Δml = 0 or +/- 1, and Δms = 0. However, there is confusion about the selection rule for terms, particularly with the acceptable transition of ΔL = 0. It is explained that while Δl cannot be 0 and Δml can only be 0 or +/- 1, it is possible to rearrange the orientation of the vectors l1 and l2 in a way that changes one of the l values by 1
  • #1
joris_pixie
25
0
Transition in LS-coupling confusion ! :)

Hello :)
Lets take for example a 2 electron system with l1,s1 and l2,s2. One electron changes energy due to electric dipole.

I understand the rules for electrons in electric dipole transitions:
1) Δl = +/- 1 (parity flips)
2) Δml = 0 or +/- 1
3) Δms = 0

But I don't get a selection rule for the terms !

One of the acceptable transitions is :
ΔL = 0
But if (1) Δl can't be 0 and (2) Δml = 0 or +/- 1 how is this possible ? :)

Because to my understanding L = l1 + l2 in vector form.
 
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  • #2
joris_pixie said:
One of the acceptable transitions is :
ΔL = 0
But if (1) Δl can't be 0 and (2) Δml = 0 or +/- 1 how is this possible ? :)

Because to my understanding L = l1 + l2 in vector form.
It is possible to rearrange the orientation of the vectors l1 and l2 such that one of the l changes by 1 while the vector sum L doesn't change its magnitude.
 

Related to Transition in LS-coupling confusion

1. What is transition in LS-coupling confusion?

Transition in LS-coupling confusion refers to the phenomenon where there is uncertainty or confusion about the energy level transitions in atoms and ions due to the coupling of the orbital angular momentum (L) with the spin angular momentum (S).

2. How does LS-coupling relate to electron energy levels?

LS-coupling is a method used to describe the energy levels of electrons in atoms and ions. It takes into account the coupling of the orbital and spin angular momenta of the electrons, resulting in a more accurate description of the energy levels compared to other methods.

3. What causes the confusion in LS-coupling?

The confusion in LS-coupling arises because the energy levels of electrons in atoms and ions are not always easily distinguishable due to their complex interactions. This can lead to difficulty in identifying the correct energy levels and transitions.

4. How is LS-coupling used in spectroscopy?

LS-coupling is a crucial concept in spectroscopy as it helps to explain the patterns observed in atomic and molecular spectra. By considering the coupling of the orbital and spin angular momenta of electrons, LS-coupling allows for a more accurate prediction of the energy levels and transitions in spectroscopic experiments.

5. Are there any limitations to LS-coupling in describing electron energy levels?

While LS-coupling is an important and widely used method in describing electron energy levels, it does have its limitations. It does not take into account the effects of electron-electron interactions, which can become significant in heavier atoms. In these cases, other methods such as intermediate coupling or j-j coupling may be used.

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